1. The Field of the Invention
The present invention relates to containers for storage of solid hazardous waste materials. More particularly, the present invention is directed to containers prepared from cementitious materials capable of long-term safe storage of certain highly toxic and nuclear waste materials.
2. Technology Review
In recent years, the public has become more sensitive to the environment and the effect of hazardous and toxic waste materials on the environmental ecosystem. Nuclear waste materials are some of the most dangerous toxic wastes because they can remain radioactive for extremely long periods of time. There is, therefore, a serious need for effective longterm storage containers for nuclear and other hazardous waste materials.
Much of the nuclear waste materials which needs to be disposed of includes refuse from nuclear weapons plants, civilian power plants, and medical industry sources. Unlike spent fuel rods which decay by emitting high level gamma radiation, the plutonium waste from weapons plants decays by penetrate paper. As a result, the plutonium waste materials from weapons plants may be handled without protective clothing and pose no danger, as long as they remain sealed. Nevertheless, plutonium is extremely toxic and very long-lived lived. In addition, it is estimated that sixty percent (60%) of the plutonium-contaminated waste from weapons plants is also tainted with hazardous chemicals such as industrial solvents.
Gloves, shoes, uniforms, tools, floor sweepings, and sludge contaminated with radioactive materials while manufacturing nuclear warheads are typically contained in 55 gallon steel drums. The Waste Isolation Pilot Project ("WIPP") site near Carlsbad, N.M., is one possible disposal site for such waste materials. The WIPP site was excavated in a massive underground salt formation. Underground salt formations, such as the WIPP site, are considered as possible permanent nuclear waste disposal sites because of the long-term stability of the underground formation and because salt has a low water permeability.
In one possible disposal plan using underground disposal sites for low-level nuclear waste materials, the underground rooms are filled with the waste containers and back-filled with a grout material to fill as much empty space as possible During the first 100 years, the underground storage rooms would collapse and crush the waste containers.
One problem with conventional 55 gallon steel drums is Eventually, the drums will be crushed when the storage room collapses; however, the presence of empty spaces permits ground water to seep into the cavities which can cause corrosion of the steel drum and decomposition of organic waste materials. Since the disposal site is not completely sealed until the underground storage room collapses and fills all void spaces, rapid collapse of the storage room is desirable so that the disposal site is sealed quickly.
Another disadvantage of conventional 55 gallon steel drums is that they are potentially capable of undergoing corrosion which would produce gases, especially H.sub.2, and which may lead to high pressure bubbles. Corrosion and its related gas evolution are considered long term liabilities. Corrosion is caused by groundwater, usually containing high concentrations of dissolved ions (i.e., 1 to 2 molar). If the hazardous waste includes organic materials, such as contaminated rubber and certain waste solvents, carbon dioxide gas may be produced which may also lead to high pressure bubbles.
Only recently has the need to avoid formation of the so-called high pressure bubbles been recognized. Current government regulations of long-term hazardous waste storage sites assume that at some time over the storage lifetime, the storage medium will be breached by underground drilling devices. If high pressure bubbles exist at the location where the storage medium is breached, then it is possible that contaminated materials may be inadvertently released under pressure.
An ideal solid hazardous waste container should satisfy some of the following characteristics: (1) the container should be made of a nonmetal or other material which intrinsically does not corrode and produce gases; (2) the container should be inexpensive; (3) the container should be impermeable to water and, if water does penetrate the container, it should act as an H.sub.2 O getter, i.e.. it should combine with water to form an insoluble solid; (4) the container should have CO.sub.2 getter characteristics, i.e., it should react with CO.sub.2 to form a solid; and (5) the container should be of a material which expands if for any reason aqueous solution does breach the impermeable outer layer. Expansion of the material on contact with water seals and fills any cracks in the container wall and also fills any space between the storage container and the walls of the salt mine which collapse around the container.
From the foregoing, it will be appreciated that what is needed in the art are containers for storing solid hazardous waste which are constructed of nonmetal materials which do not intrinsically corrode to produce a gas.
Additionally, it would be a significant advancement in the art to provide containers for storing solid hazardous waste which are H.sub.2 O and CO.sub.2 getters.
It would be a further advancement in the art to provide containers for storing solid hazardous waste constructed of materials which expand upon contact with aqueous solution to fill holes and thereby inhibit further aqueous solution penetration into the container.
Finally, it would be an important advancement in the art to provide containers for solid hazardous waste which are inexpensive.
Such solid hazardous waste containers are disclosed and claimed herein.